The present invention is directed to an ejector assembly for use with a mold for molding plastic parts and, in particular, to a lifter foot assembly for removal of a core block from the mold.
When molding a plastic part having an undercut feature underneath the part, it is necessary to eject the part from the mold in a compound motion. The motion involves lateral movement as well as movement away from the mold surface. This may be accomplished by a core blade lifter in the form of a lifter rod which is mounted at an angle to the ejector plate by a lifter foot assembly that is capable of traveling laterally along the ejector plate. This allows the ejector plate end of the lifter rod to move laterally as the ejector plate is actuated.
For certain part designs, the amount of undercut requires that the lifter rod be mounted at a more extreme angle with respect to the direction of movement of the ejector plate. Such extreme angle places additional force on the foot assembly which could result in failure or excessive wear to the lifter rod and/or the lifter foot assembly.
Designing an ejector assembly has traditionally been a time-consuming task. The lifter foot assembly has to be machined to accommodate the angle of the lifter rod. Moreover, if it desired to control the acceleration of the lifter rod during the ejection of the part, it is common to provide a slight increase or decrease in elevation up the lifter rod with respect to the ejector plate during the lateral motion of the lifter rod. This also must be calculated and specifically machined into the lifter foot assembly.